The present invention relates generally to the field of electronic detection apparatus and more particularly to a system for the detection of objects concealed within and close to the surface of the earth. The predominant current usage of the minefield reconnaissance and detector system of the present invention is as a means for detecting surface and subsurface ordnance and the like concealed in a subject field.
The detection of concealed mines has been a subject of great interest among military personnel. Similarly, practitioners in other fields have found occasion to use technology originally developed for the purpose of mine detection. An example is the detection of buried toxic waste containers during toxic waste cleanup operations. The most widely practiced technology has been conventional "metal detector" devices which are carried by an operator and which provide the operator with an audible and/or visible signal roughly corresponding to the disruption of a magnetic field occasioned by a ferromagnetic object. A disadvantage of this approach has been that the operator is required to make decisions about whether the received signal is truly indicative of a buried mine. This is particularly difficult because the signal strength varies not only with the size of a buried object, but also with the depth at which the object is buried, the material composition of the object, and the characteristics of the soil in which the object is buried. In short, the probability of a wrong decision is appreciable and, given that such conventional prior art devices are usually carried upon the person of the operator, the consequences of a "false negative" decision while searching for buried land mines can indeed be grave.
A possible improvement to conventional methods for mine detection which has been tried has been to remove the operator from the vicinity of the detector apparatus. However, attempts to accomplish this have previously been less than successful. It would seem that this simple expedient must be tied to some improvement in the data gathering and decision making processes in order to be successful, if for no other reason than the fact that the removal of the operator from the area of danger may have some effect on the operator's willingness to commit to decisions.
Attempts to advance the art have involved the use of different technologies, such as radar and infra-red detection devices. To the inventors' knowledge, this approach has not resulted in an improved mine detection apparatus, since these technologies have not proven to be generally superior to conventional metal detector technology for the purpose. Furthermore, attempts to combine technologies have only resulted in an increased likelihood of "false positive" indications, to the extent that such combinations have been impractical to use. All such attempts to supplement one technology with another for this purpose, to the inventors' knowledge, have merely provided alternative sensing means, any one of which might provide an indication that a mine is present. Therefore, such attempts have resulted in a greatly increased number of false positive indications without providing the benefit of a sufficiently decreased number of false negative indications. It is important to note that all such prior attempts to combine technologies for this purpose within the inventors' knowledge have been within the realm of undisclosed experiments within the project which has resulted in the present invention and, thus, are not prior art with respect to the present invention.
All of the prior art mine detection systems within the inventors' knowledge have merely provided data which must be interpreted by a human operator, or else have been subject to an unacceptable rate of false positive or false negative errors.
No prior art mine detection system to the inventors' knowledge has successfully gathered and analyzed data so as to provide a reliable yes/no (mine/no mine) indication to an operator. All successful applications to date have required human decision making and the stress and potential for human error attendant thereto, or else have been subject to an unacceptable error rate.